一个新的与稻瘟病菌无毒基因AVR-Pik^m紧密连锁的SCAR标记

A novel SCAR marker closely linked to the avirulence gene AVR-Pik^m in rice blast fungus Magnaporthe grisea

无毒基因是病原物中决定寄主抗病性表达的功能基因,其功能的丧失导致毒性小种的产生。本研究利用随机引物扩增DNA多态性技术,从稻瘟病菌菌株S1522中新筛选到1个与无毒基因AVR-Pikm紧密连锁的DNA标记OPE121400。根据OPE121400的核苷酸序列,设计了1对含有17个核苷酸的特异性SCAR引物,并利用该引物对无毒表型亲本S1522和毒性表型亲本S159及其有性杂交后代的108个菌株进行了PCR扩增。结果表明:所有无毒表型的菌株均能特异性扩增出1条与OPE121400大小相近的DNA片段,而毒性表型的菌株除2个重组体外,均不能扩增出此片段。根据计算,这一SCAR标记与目标无毒基因AVR-Pikm之间的遗传距离为1.89 cM,与本研究小组先前报道的另一个标记OPO121000位于目标基因的同一侧,但与OPO121000相比,距目标基因近了2.86 cM。本标记的获得将有助于确定AVR-Pikm在染色体上的位置,有助于确定用于进一步筛选位于相反一侧的连锁标记的重叠群区域。

Avirulence genes are functional genes in pathogens that determine expression of the race-specific resistance in hosts. By using the technique of random amplified polymorphic DNAs(RAPD), this study identified a new DNA marker OPEl21400 that was closely linked to the avirulence gene, AVR-Pikm, in rice blast pathogen Magnaporthe grisea. Based on the nucleotide sequence of OPE121400 a pair of 17 nt primers was designed and used for PCR detection of DNA polymorphism in a mapping population, which was generated by crossing an avirulent strain S1522 with a virulent strain S159. A single DNA band with similar length to the RAPD marker OPE121400 was generated by the PCR in all the avirulent progenies but not in the virulent ones except for two recombinants. The genetic distance from the marker to AVR-Pikm was calculated as 1. 89 cM, which was 2. 86 cM closer to the gene than OPO121000, a RAPD marker previously identified by our group. Although lied in the same side with OPO121000, OPE121400 will be useful for locating the position of AVR-Pikm in the chromosome and orientating contigs for further screening of linked SSR markers that lie in the opposite side.